Computer scale-out method, computer system, and storage medium

Abstract

A computer scale-out method by adding a second computer to a first computer receiving stream data from a data source and executing a query to make the second computer execute the query, the computer scale-out method including: receiving, by a management computer, a request to scale out; a second step of generating, by the management computer, rewritten queries that are copies of the query; sending, by the management computer, instructions to scale out including the rewritten queries to the first computer and the second computer; receiving, by the first computer and the second computer, the instructions to scale out, extracting the rewritten queries, and switching to the extracted rewritten queries; notifying, by the first computer or the second computer, the management computer of readiness of the rewritten queries; and sending, by the management computer, an instruction to add the second computer as a destination to the data source.

What is claimed is: 
     
         1 . A computer scale-out method by adding a second computer to a first computer receiving stream data from a data source and executing a query to make the second computer execute the query, the computer scale-out method comprising:
 a first step of receiving, by a management computer connected with the first computer and the second computer, a request to scale out;   a second step of generating, by the management computer, rewritten queries that are copies of the query in which when to execute the query is rewritten;   a third step of sending, by the management computer, instructions to scale out including the rewritten queries to the first computer and the second computer;   a fourth step of receiving, by the first computer and the second computer, the instructions to scale out, extracting the rewritten queries, and switching to the extracted rewritten queries;   a fifth step of notifying, by the first computer or the second computer, the management computer of readiness of the rewritten queries; and   a sixth step of sending, by the management computer, an instruction to add the second computer as a destination of the stream data to the data source to make the data source send the same stream data to the first computer and the second computer.   
     
     
         2 . The computer scale-out method according to  claim 1 , wherein the fourth step further includes:
 a step of switching, by the first computer, the query being executed to one of the rewritten queries; and   a step of starting, by the second computer, executing another rewritten query.   
     
     
         3 . The computer scale-out method according to  claim 2 , wherein, in the second step, the rewritten queries include a first rewritten query to change the query executed by the first computer to be executed in a first execution timing mode and a second rewritten query to be executed by the second computer in a second execution timing mode. 
     
     
         4 . The computer scale-out method according to  claim 3 , wherein the first execution timing mode and the second execution timing mode are configured to alternately provide outputs from the first rewritten query and outputs from the second rewritten query. 
     
     
         5 . The computer scale-out method according to  claim 4 , wherein, in a case where a window size of the query is specified with time, the first timing mode and the second timing mode are configured so that time intervals to provide outputs from the first rewritten query alternate with time intervals to provide outputs from the second rewritten query. 
     
     
         6 . The computer scale-out method according to  claim 4 , wherein, in a case where a window size of the query is specified with number of tuples of stream data, the first timing mode and the second timing mode are configured so that tuples output from the first rewritten query alternate with tuples output from the second rewritten query. 
     
     
         7 . The computer scale-out method according to  claim 1 ,
 wherein the first step further includes a step of selecting, by the management computer, a query to be scaled out, and   wherein the second step further includes a step of generating, by the management computer, rewritten queries of the selected query.   
     
     
         8 . The computer scale-out method according to  claim 1 , wherein the fourth step further includes a step of synchronizing execution environments for the rewritten queries between the first computer and the second computer. 
     
     
         9 . The computer scale-out method according to  claim 8 ,
 wherein the third step further includes a step of making the data source stop sending stream data, and   wherein the sixth step further includes a step of making the data source resume sending stream data.   
     
     
         10 . The computer scale-out method according to  claim 8 , wherein the sixth step further includes a step of inserting a tuple for triggering switching processing to use the rewritten queries into the stream data. 
     
     
         11 . A computer system comprising:
 a first computer configured to receive stream data from a data source and execute a query; and   a management computer configured to add a second computer for executing the query of the first computer,   wherein the management computer is configured to, upon receipt of a request to scale out, generate rewritten queries in which when to execute the query is rewritten as copies of the query and send instructions to scale out including the rewritten queries to the first computer and the second computer,   wherein the first computer and the second computer are configured to, upon receipt of the instructions to scale out, extract the rewritten queries, switch to the extracted rewritten queries, and notify the management computer of readiness of the rewritten queries, and   wherein the management computer is configured to send an instruction to add the second computer as a destination of the stream data to the data source to make the data source send the same stream data to the first computer and the second computer.   
     
     
         12 . The computer system according to  claim 11 , wherein the first computer is configured to switch the query being executed to one of the rewritten queries and the second computer is configured to start executing another rewritten query. 
     
     
         13 . The computer system according to  claim 12 , wherein the rewritten queries include a first rewritten query to change the query executed by the first computer to be executed in a first execution timing mode and a second rewritten query to be executed by the second computer in a second execution timing mode. 
     
     
         14 . The computer system according to  claim 13 , wherein the first execution timing mode and the second execution timing mode are configured to alternately provide outputs from the first rewritten query and outputs from the second rewritten query. 
     
     
         15 . A computer-readable non-transitory storage medium storing a program configured to be run on a computer including a processor and a memory, the program being configured to add a second computer to a first computer receiving stream data from a data source and executing a query to make the second computer execute the query by making the computer execute:
 a first step of receiving a request to scale out;   a second step of generating rewritten queries that are copies of the query in which when to execute the query is rewritten;   a third step of sending instructions to scale out including the rewritten queries to the first computer and the second computer to make the first computer and the second computer switch to the rewritten queries;   a fourth step of receiving a notice of readiness of the rewritten queries from the first computer or the second computer; and   a fifth step of sending an instruction to add the second computer as a destination of the stream data to the data source to make the data source send the same stream data to the first computer and the second computer.